Hey guys i have been trying to fix an annoying cold start stumble with my car since i have had it. When i start the car it hunts for an idle for a minute or two and then will usually die. I start it up again and when i start to drive away it stumbles and then takes off. As soon as it warms up it runs ok. I mean ok because even after its warmed up its still got a shaky idle. Nothing like when its cold but still shakey. So far i have repalced the cap and rotor(msd),fuel filter,Spark plugs(ac rapidfires), new maf relays(threw the code).I still need to replace the plug wires but i dont think they are the problem. Im getting no codes. ANd its been running rich. My timing is bumped aobut 6* but did this even before the advance. Might be a sensor? Any ideas

Ps. Did a search but theirs just to many problems like this to pinpoint one specifically if i missed it im sorry Thanks

 

If there are no codes prevalent, you might want to check you're compression, as well as check the intake for any vacuum leakage.

Was this a problem 'before' you swapped to new spark-plugs? I only ask, because I had a similar problem with aftermarket spark-plugs.... the engine would idle really rough, then stall, with no codes being thrown whatsoever. Turns out the plugs weren't gapped correctly, but this 'might' not be with you're situation though.

 

no i prechecked the gaps before hand and the car did this even before the plug change. Im really confused on this.

 

If you are running rich, you probably want to find out why. If you have a scan tool available to you, take a look at what the temp sensor has to say. (not the one in the dash.....) It is possible the sensor is failing, and giving false readings. This can cause all sorts of interesting problems.........

Have you reset minimum air? TPS? There are articles available on this website on both of these procedures. I highly recommend them. (look in the tech articles section......)

You may also want to see that your TPS does not have any "flat spots". Confuses Mr. ECM to no end...... Scan tool required for this as well. (well, I suppose it is possible to do this with a VOM, but, the scan tool makes it SO much easier..... IMHO)

Good Luck

 

well i currently dont have a scan tool so im not sure i can get a reading on the sensor. Ill check the tps and put the timing back to normal but i still dont think this will help cuz it ran rich and stumbled at cold even before the advance. Can a bad spark wire or two cause this because 3 of them werent replaced during the last tune-up(kid i bought it off of never changed them for some reason)Also when going up a hill with very light car the car will stumble or miss for a second. Doesnt feel like its dying jsut misses for a second. The only thing i noticed was that a gasket between the intake and the runners was sticking up a bit. I think the kid i bought it off of put it on upside down or did not align it properly. its not bad jsut sticking up a bit. Can this cause problems.

 

Try the O2 sensor too, and a temp sensor is only about $7 so that would be some cheap troubleshooting to replace it and see what that does for you.

 

Running rich all the time could be an O2 sensor, but since the problem is prevelant when the car is cold too I'd probably say that the O2 isn't a problem, because during warmup the ECM isn't taking a reading from the O2.

It could be a temp sensor too, fooling the ECM into thinking that the car isn't up to operating temp and keeping it under warm up enrichment.

Definately replace your wires too. They can cause all kinds of wierd intermitten problems.

The TPS and IAC are both places to investigate too. Can you keep it from stalling by feeding it throttle?

A faulty VSS could also cause similar problems, and they don't throw a code when they go bad...

 

Well the car seems to be running a bit rich all the time so i think im jsut gonna go ahead and replace the o2 sensor while im putting in the plug wires. The car only stumbles when cold and if i give it a bit of gas it will stumble and then rev real fast and take off. What is the Vss? The car stumbled and ran the same way even in 80 degree weather.(right now its about 10 degrees up here in Chi Town).Im gonna replace the temp sensor and see if that helps along with setting the tps and timing back to stock. Ill post back and see what happens. Thanks for the help guys

 

The VSS is the vehicle speed sensor. It also runs the speedo in electronic speedo cars, so your speedo wouldn't work if the VSS was bad. Mechanical speedo cars also have one built into the speedo housing. There's no real way to tell if it fails, except that the car may start running poorly.

Get everything back to stock and see what happens.

If it's still the same try turning the idle screw in a full turn and see if the problem gets any better. You'll need to readjust your TPS voltage when you do this. If this makes an improvement then a bad VSS is almost certainly the cause.

 

If the temp sensor is bad wouldn't the gauge in the car be messed up???

 

Maroguy1,

You're thinking about the engine temp sensor that is located near the #1 sparkplug. He is talking about the coolant temp sensor mounted under the throttle body.

The Trickster!!!!!!!!!!!